Phospholipids, such as lecithin or phosphatidylcholine, consist of glycerol esterified with two fatty acids in an outer (sn-1) and the middle (sn-2) positions and esterified with phosphoric acid in the third position; the phosphoric acid, in turn, may be esterified to an amino-alcohol. Phospholipases are enzymes which participate in the hydrolysis of phospholipids. Several types of phospholipase activity can be distinguished, including phospholipase A1 and A2 which hydrolyze one fatty acyl group (in the sn-1 and sn-2 position, respectively) to form lysophospholipid; and lysophospholipase (or phospholipase B) which can hydrolyze the remaining fatty acyl group in lysophospholipid. This invention relates to a phospholipase that has the ability to hydrolyze both fatty acyl groups in a phospholipid. Enzymes with this activity are also some times called phospholipase B.
Enzymes with phospholipase B activity have been reported from various fungal sources, including Penicillium notatum (also known as P. chrysogenum; N. Kawasaki, J. Biochem., 77, 1233-44, 1975; N. Masuda et al., Eur. J. Biochem., 202, 783-787, 1991), Saccharomyces cerevisiae (M. Ichimasa et al., Agric. Biol. Chem., 49 (4), 1083-89, 1985; F. Paultauf et al., J. Biol. Chem., 269, 19725-30, 1994), Torulaspora delbrueckii (old name Saccharomyces rosei; Y. Kuwabara, Agric. Biol. Chem., 52 (10), 2451-58, 1988; FEMS, Microbiol. Letters, 124, 29-34), Schizosaccharomyces pombe (H. Oishi et al., Biosci. Biotech. Biochem., 60 (7), 1087-92, 1996), Aspergillus niger (Technical Bulletin, G-zyme.TM. G999, Enzyme Bio-Systems Ltd.) and Corticium centrifugum (S. Uehara et al., Agric. Biol. Chem., 43 (3), 517-525, 1979).
It is known to use phospholipase in, e.g., enzymatic oil degumming (U.S. Pat. No. 5,264,367, Metallgesellschaft, Rohm), treatment of starch hydrolysate (particularly from wheat starch) to improve the filterability (EP 219,269, CPC International) and as an additive to bread dough to improve the elasticity of the bread (U.S. Pat. No. 4,567,046, Kyowa Hakko).
It is the object of this invention to provide an improved phospholipase for use in such processes.